Traditional receiver front-end generally requires external surface acoustic wave (SAW) filters to filter out-of-band blockers and interferences. However, the off-chip components of SAW filter are usually bulky, inflexible and expensive. To decrease cost and form factor while improving integration and system performance, SAW-less receiver front-end has been widely studied and reported in public domain. However, most of them focus on applications below 3 GHz, which is not applicable for higher frequencies, for example, 802.11ac Wireless Local Area Network (WLAN). Moreover, due to ubiquitous parasitic effects, especially parasitic capacitance, the actual working frequency will not be the same as desired. Especially when working at higher frequencies, the working frequency will be shifted downwards a lot.
Therefore, there is a need of providing a low noise amplifier to obviate the drawbacks encountered from the prior arts.